Swelling affects quads strength up to 4 years post knee injury/surgery – what can you about it?

After knee injury, surgery and pathology, it’s common both as a patient and a clinician to see marked weakness of the quadriceps muscles at the front of the thigh, even following extended periods of rehabilitation. This is partly due to muscle wasting in some cases, but is also partly due to a phenomenon known as athrogenic muscle inhibition (AMI). AMI occurs in all cases of knee injury, regardless of the pathology. Why is important to minimize this? Because without good quadriceps strength and control, there is a decrease in lower leg control during walking and running, and an impairment in the normal stability and control of the knee during everyday activities and of course during recreational and sporting activities.

AMI seems to be worse immediately after knee injury or surgery, but it can actually persist for month, and sometime even years. What is even more interesting, is that studies have found that following knee injury or surgery, this inhibition of the quadriceps muscles occurs in the non-injured leg as well! Compared to the injured leg, there isn’t the same degree of muscle loss, but it does take just as long (sometime up to 4 years) to recede. What this means clinically, is that both patients and clinicians have to be careful when comparing strength in an injured to an un-injured leg, as both are likely to be impaired.


For a long time, it was thought that AMI was caused by pain and inflammation. It was a bit of a mystery why the quads weakness persisted long after the knee was back to feeling comfortable after an injury. It is now known that the presence of swelling in the knee, in the absence of pain and inflammation, can also cause AMI. In fact, the link between knee pain and quadriceps AMI hasn’t been clearly shown in studies. From clinical studies, it has however been found that just 10ml of fluid is enough to cause the AMI to be present. This is a very small amount indeed, and would probably not be able to be detected clinically. So we know, therefore, that the presence of knee swelling, even small amounts, can have a powerful effect on quadriceps weakness and inhibition after knee injury/surgery.

So the next important question is: what can we do therefore to minimize AMI? Again from clinical studies, it has been found that local anaesthetic or aspiration of fluid from the knee can help, but unfortunately these interventions don’t always work, nor are they practical from an everyday patient point-of-view. A really interesting piece of research has been carried out however by David Rice and colleagues at the Auckland University of Technology here in New Zealand. They found that using ice on the knee (they used bags of partially crushed ice wrapped around the knee for 20 minutes temporarily reduced the severity of AMI, thereby giving a ‘window of opportunity’ to work on strengthening. This is likely to lead to more effective and quicker strengthening of the main things to remember?

   Keep the swelling down in your knee as much as possible by following the well known principles of Rest, Ice, Compression and Elevation (RICE)

   Ice the knee for 20 mins (make sure it’s the knee you are icing, not the quads muscle itself) and then do your quadriceps strengthening exercises immediately following this

   Also work on knee stability and proprioception exercises (ask your physio about these), as they can also minimize AMI)

   In cases of severe persistent swelling, knee aspiration or anaesthetic may be required to further minimize AMI.

As always, consult your Physio or health professional for appropriate advice and exercises first. 


Rice, D., McNair, P.J., Dalbeth, N. (2008) Effects of cryotherapy on arthrogenic muscle inhibition using an experimental model of knee swelling. Arthritis Care & Research, 61 (1), 78-83.

Rice, D., Mcnair, P.J. (2010). Quadriceps arthrogenic muscle inhibition: neural mechanisms and treatment perspectives. Seminars in Arhritis and Rheumatism. 40 (3), 250-266.

Rice, D. (2008) Cryotherapy reduces arthrogenic muscle inhibition following experimental knee joint infusion. Clinical Neurophysiology, 119, 90.

9 Responses to Swelling affects quads strength up to 4 years post knee injury/surgery – what can you about it?

  1. Emiljano says:

    I tried returning to american football after 8.5 months post op but my patella was giving me pain so I had to stop. It is now 16 months post op and I had a good run of pretty much pain free practices and now it’s returning and it looks like this may be the reason why because my quad especially the medial side is weaker and noticeable from the other leg. Thanks I will follow these tips and see how it goes if you have any others I would love to hear them.

  2. Andy Schmidt says:

    I guess in your rehab time you have doing a lot of quads-specific strengthening? because of the deficits relating to swelling and pain, it really is a case of often being 2 steps forward, one step back when trying to get the return of quads strength. Ideally, you should get to about 10% of the good side. Remember too that the bulk and tone may not be there, but as long as the functional strength is, then that is ok. Good luck and keep working on it, you will get there!

  3. Anibal Pflieger says:

    Many types of minor knee pain respond well to self-care measures. Physical therapy and knee braces also can help relieve knee pain. In some cases, however, your knee may require surgical repair.”“*

  4. neha says:

    i had a knee injury where fluid had accumulated around my knee. Fluid was aspirated and my leg was immobilized for a week.My quadriceps had weakened and my doctor suggestsd physiotherapy. two years later i developed chondromalacia and doctor suggested physiotherapy. my symptoms of pain and weakness reduce while during physiotherapy(which i did for 3 months as suggested by my doctor)but when i stop my exercises my symptoms come back within a month or so. This has happened twice. i feel i like my muscles are never going to get back their strength. please help.

    • Andy Schmidt says:

      Are you able to elaborate any more on what the initial injury was at all? And I guess my other question would be, is there any reason why you stop doing the exercises?
      Kind regards

  5. WM says:

    I am a 62 year old retired firefighter with a 12 year old injury of a ruptured lower quadricep together with a small defect in the articular cartilage on the medial side. I declined surgery at the time and had my leg in a plaster cast for 6 weeks with the plaster removed I had a course of 2 local anaesthetic injections over 2 weeks followed by an aspiration of 6mls of serous fluid from the knee joint. A further 6 months of VMO rehabilitation to strengthen the knee completed the treatment. Unfortunately, the injury ended my firefighting career prematurely.

    Even know, I cannot kneel on the floor, or jog for more than 10 minutes without feeling discomfort /pain in the knee and still have tightness around the knee joint. On some occasions i still get Swelling around the knee and still have some wasting muscle in the lower quadricep.

    Do you think that my age ( 50) when the injury occurred was a contributory factor to this lack of recovery.

    Sent from my iPad, Be Happy.

    • Andy Schmidt says:

      In short..age was probably a factor, mainly because we know that unfortunately the tissues don’t heal as well as we age. Also swelling tends to be harder to get rid of, and strength harder to return too. The lack of ability to kneel and tightness around the knee joint is likely to be partly a result of deep scar tissue from the quads repairing. The intermittent knee swelling is more likely to be a result of the articular cartilage defect I suspect.
      Sorry to hear it ended your career prematurely. I guess the best I can say here is continue to make knee maintenance strengthening, balance and general core stability work an ongoing part of your exercise routine. And try and embrace other forms of cardio that don’t impact the knee as much as running does. Best of luck and hope that helps.

  6. Abraham says:

    I had a MPFL reconstruction a year ago, following the surgery i started physical therapy for about four months and then started working out at the gym lifting weights. So far i haven’t recovered my quad strenght completely, after a year i feel kind of stuck i guess it’s due to AMI keeping me from getting stronger quad.
    I’m still doing exercises everyday and some jogging on weekends but frustrated because i’m stuck at 3/5 of quad strenght.
    I’d like to know if this is normal, will i eventually get fully recovered in the long run or this is a point of no return. what should i do?

    Sorry about my english.

    Thanks in advance.

    • Andy Schmidt says:

      How often are you doing your quads exercises – and have you had a physiotherapsit check them regularly to double check that you are isolating your quadriceps? normally after 1 year you would expect about 80-90% of your quads strength to have returned, if you have been really diligent with the rehab…let me know. thanks, Andy

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